Nanocrystal particles and processes for synthesizing the same

ABSTRACT

A nanocrystal particle including at least one semiconductor material and at least one halogen element, the nanocrystal particle including: a core comprising a first semiconductor nanocrystal; and a shell surrounding the core and comprising a crystalline or amorphous material, wherein the halogen element is present as being doped therein or as a metal halide

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application of U.S. Pat. ApplicationSerial No. 15/830,134, filed on Dec. 4, 2017, which is a continuation inpart application of U.S. Patent Application Serial No. 14/494,673, filedon Sep. 24, 2014, which claims priority to and the benefit of KoreanPatent Applications Nos. 10-2013-0114601 and 10-2014-0124542, filed onSep. 26, 2013, and Sep. 18, 2014, respectively, and all the benefitsaccruing therefrom under 35 U.S.C. §119, the contents of which areincorporated herein in their entirety by reference.

BACKGROUND 1. Field

A nanocrystal particle and a process for synthesizing the same aredisclosed.

2. Description of the Related Art

Unlike bulk materials, nanocrystals have physical characteristics (e.g.,energy bandgap and melting point) that are an intrinsic property oftheir particle size. For example, a semiconductor nanocrystal (alsoknown as a quantum dot) is a semiconductor material having a crystallinestructure of a size of several nanometers. The semiconductor nanocrystalhas a very small size and a large surface area per unit volume and mayexhibit a quantum confinement effect. Therefore, the semiconductornanocrystal has different physicochemical characteristics than the bulkmaterial having the same composition. In other words, the nanocrystalmay have selected characteristics by selecting its size. A quantum dotmay absorb light from an excitation source to be in an excited state,and may emit energy corresponding to its energy bandgap.

The semiconductor nanocrystal may be synthesized by a vapor depositionmethod such as metal organic chemical vapor deposition (“MOCVD”) ormolecular beam epitaxy (“MBE”), or by a wet chemical method of adding aprecursor to an organic solvent to grow crystals. In the wet chemicalmethod, organic materials, such as a dispersant, are coordinated to asurface of the semiconductor crystal during the crystal growth tocontrol the crystal growth. Therefore, the nanocrystals produced by thewet chemical method usually have a more uniform size and shape thanthose produced by the vapor deposition method.

Semiconductor nanocrystal materials having a core-shell structure mayexhibit slightly enhanced quantum efficiency. Nonetheless, there remainsa need for technologies having enhanced qualities, such as improvedquantum efficiency.

SUMMARY

An embodiment provides a semiconductor nanocrystal having enhanced lightemitting properties, such as a high quantum yield.

Another embodiment provides a process of preparing the semiconductornanocrystal having enhanced light emitting properties.

In an embodiment, a nanocrystal particle includes at least onesemiconductor material and at least one halogen element, and has acore-shell structure including a core of a first semiconductornanocrystal, and a shell surrounding the core and including acrystalline or amorphous material, The at least one halogen element maybe present as being doped in the particle (e.g., in an elemental form)or as a metal halide.

The halogen element may be substituted in the crystalline structure ofthe nanoparticle or may be introduced therein as an interstitial atom.

The at least one halogen element may comprise fluorine (F).

The first semiconductor nanocrystal may include a metal selected from aGroup II metal, a Group III metal, a Group IV metal, and a combinationthereof, and the crystalline or amorphous material may include at leastone metal which is different from the metal included in the firstsemiconductor nanocrystal and which is selected from a Group I metal, aGroup II metal, a Group III metal, a Group IV metal, and a combinationthereof.

The first semiconductor nanocrystal may include a first semiconductormaterial, and the crystalline material of the shell may include a secondsemiconductor material that is deposited on the core and that isdifferent from the first semiconductor material.

The halogen element may be included in the core, and/or the halogenelement may be present at an interface between the core and the shell,and/or the halogen element may be present in the shell.

The shell may be a multi-layered shell having at least two layers, eachof the layers including the same or different crystalline or amorphousmaterials, and the halogen element may be present in a region selectedfrom the core, in an inner shell (i.e., an inner layer of the shell), inan outer shell (i.e., an outer layer of the shell being on the innerlayer), at an interface between the core and the shell, at an interfacebetween the layers of the shell, and a combination thereof. The halogenelement may be present in all of the aforementioned regions.

The halogen element may be included in an amount of greater than orequal to about 0.05 mole percent, based on a total molar amount of themetal of the core of the nanocrystal particle. The halogen element maybe included in an amount of less than or equal to about 200%, forexample, less than or equal to about 190%, less than or equal to about180%, less than or equal to about 170%, less than or equal to about160%, less than or equal to about 150%, less than or equal to about140%, less than or equal to about 130%, less than or equal to about120%, less than or equal to about 110%, or less than or equal to about100% based on a total molar amount of the metal of the core of thenanocrystal particle.

The halogen element may be fluorine, and it may be present in a formselected from a fluoride including a Group I metal, a fluoride includinga Group II metal, a fluoride including a Group III metal, and acombination thereof.

The first semiconductor nanocrystal of the core may include a GroupII-VI compound, a Group III-V compound, a Group IV-VI compound, a GroupIV compound, or a combination thereof, and the crystalline or amorphousmaterial of the shell may include a Group II-VI compound, a Group III-Vcompound, a Group IV-VI compound, a Group IV compound, a halogencompound containing a metal and a halogen, a metal oxide, or acombination thereof.

The crystalline or amorphous material may include a metal which isdifferent from the metal included in the first semiconductornanocrystal.

The Group II-VI compound may be selected from:

-   a binary element compound selected from CdSe, CdTe, ZnS, ZnSe, ZnTe,    ZnO, HgS, HgSe, HgTe, MgSe, MgS, and a combination thereof;-   a ternary element compound selected from CdSeS, CdSeTe, CdSTe,    ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe,    CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, and a    combination thereof; and-   a quaternary element compound selected from HgZnTeS, CdZnSeS,    CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe,    HgZnSTe, and a combination thereof.

The Group III-V compound may be selected from:

-   a binary element compound selected from GaN, GaP, GaAs, GaSb, AlN,    AlP, AlAs, AlSb, InN, InP, InAs, InSb, and a combination thereof;-   a ternary element compound selected from GaNP, GaNAs, GaNSb, GaPAs,    GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs,    InPSb, and a combination thereof; and-   a quaternary element compound selected from GaAlNP, GaAlNAs,    GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs,    GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and a    combination thereof.

The Group IV-VI compound may be selected from:

-   a binary element compound selected from SnS, SnSe, SnTe, PbS, PbSe,    PbTe, and a combination thereof;-   a ternary element compound selected from SnSeS, SnSeTe, SnSTe,    PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and a combination    thereof; and-   a quaternary element compound selected from SnPbSSe, SnPbSeTe,    SnPbSTe, and a combination thereof.

The Group IV compound may be selected from:

-   a singular element selected from Si, Ge, and a combination thereof;    and-   a binary element compound selected from SiC, SiGe, and a combination    thereof.

The crystalline or amorphous material in the shell may include ZnSe,ZnS, ZnSeS, or a combination thereof.

The nanocrystal particle may comprise a bond between the zinc and thefluorine.

The halogen compound containing a metal and a halogen may be selectedfrom LiF, NaF, KF, BeF₂, MgF₂, CaF₂, SrF₂, CuF, AgF, AuF, ZnF₂, CdF₂,HgF₂, AlF₃, GaF₃, InF₃, SnF₂, PbF₂, LiCl, NaCl, KCl, BeCl₂, MgCl₂,CaCl₂, SrCl₂, CuCl, AgCl, AuCl, ZnCl₂, CdCl₂, HgCl₂, AlCl₃, GaCl₃,InCl₃, SnCl₂, PbCl₂, LiBr, NaBr, KBr, BeBr₂, MgBr₂, CaBr₂, SrBr₂, CuBr,AgBr, AuBr, ZnBr₂, CdBr₂, HgBr₂, AlBr₃, GaBr₃, InBr₃, SnBr₂, PbBr₂, LiI,NaI, KI, BeI₂, MgI₂, CaI₂, SrI₂, CuI, AgI, AuI, ZnI₂, CdI₂, HgI₂, AlI₃,GaI₃, InI₃, SnI₂, PbI₂, and a combination thereof.

The metal oxide may be selected from the group consisting of CdO, In₂O₃,PbO, HgO, MgO, Ga₂O₃, Al₂O₃, ZnO, SiO₂, zinc oxysulfide, zincoxyselenide, zinc oxysulfide selenide, indium phosphide oxide, indiumphosphide oxysulfide, and a combination thereof.

The shell may include a material having a composition different fromthat of the first semiconductor nanocrystal, and having a larger bandgapthan that of the first semiconductor nanocrystal.

The nanocrystal particle may have a ligand compound coordinating asurface thereof.

The ligand compound may include RCOOH, RNH₂, R₂NH, R₃N, RSH, R₃PO, R₃P,ROH, RCOOR′, RPO(OH)₂, R₂POOH, or a combination thereof, wherein R andR′ are each independently selected from a C1 to C24 alkyl group, a C2 toC24 alkenyl group, and a C6 to C20 aryl group.

In another embodiment, a process of synthesizing a nanocrystal particleincludes:

-   obtaining a first mixture including a first precursor, a ligand    compound, and a solvent;-   optionally heating the first mixture;-   contacting a halogen source (i.e., a source of a halogen element), a    second precursor, and optionally a first nanocrystal with the first    mixture, which is optionally heated, to obtain a second mixture; and-   heating the second mixture to a reaction temperature to react the    first precursor and the second precursor to obtain a nanocrystal    including a semiconductor material and the halogen element.

In the above process, the first precursor may be two or more differentcompounds and/or the second precursor may be two or more differentcompounds. These compounds may be added in any order or in the form of amixture, for example, with a ligand compound and/or a solvent.

The first precursor may include a Group II metal, a Group III metal, aGroup IV metal, or a combination thereof, and may be in the form of anelemental metal (i.e., a metal powder), an alkylated metal compound, ametal alkoxide, a metal carboxylate, a metal nitrate, a metalperchlorate, a metal sulfate, a metal acetylacetonate, a metal halide, ametal cyanide, a metal hydroxide, a metal oxide, a metal peroxide, or acombination thereof, and the second precursor may include a Group Velement, a Group VI element, a compound including the Group V element orthe Group VI element, a compound containing a halogen element, or acombination thereof.

The Group V element, the Group VI element and the compound containing aGroup V element or a Group VI element may be selected from sulfur (S),selenium (Se), selenide, tellurium, telluride, phosphorous (P), arsenic(As), arsenide, nitrogen (N), hexanethiol, octanethiol, decanethiol,dodecanethiol, hexadecanethiol, mercaptopropylsilane,sulfur-trioctylphosphine (“S-TOP”), sulfur-tributylphosphine (“S-TBP”),sulfur-triphenylphosphine (“S-TPP”), sulfur-trioctylamine (“S-TOA”),bis(trimethylsilyl)sulfide, ammonium sulfide, sodium sulfide,selenium-trioctylphosphine (“Se-TOP”), selenium-tributylphosphine(“Se-TBP”), selenium-triphenylphosphine (“Se-TPP”),tellurium-tributylphosphine (“Te-TBP”), tellurium-triphenylphosphine(“Te-TPP”), tris(trimethylsilyl)phosphine, tris(dimethylamino)phosphine,triethylphosphine, tributylphosphine, trioctylphosphine,triphenylphosphine, tricyclohexylphosphine, arsenic oxide, arsenicchloride, arsenic sulfate, arsenic bromide, arsenic iodide, nitricoxide, nitric acid, ammonium nitrate, and a combination thereof.

The ligand compound may include a compound represented by RCOOH, RNH₂,R₂NH, R₃N, RSH, R₃PO, R₃P, ROH, RCOOR′, RPO(OH)₂, or R₂POOH, or acombination thereof, wherein R and R′ are independently selected from aC1 to C24 alkyl group, a C2 to C24 alkenyl group, and a C6 to C20 arylgroup.

The solvent may be selected from a C6 to C22 primary amine, a C6 to C22secondary amine, C6 to C40 tertiary amine, a heterocyclic compoundhaving a nitrogen atom, a C6 to C40 olefin, a C6 to C40 aliphatichydrocarbon, a C6 to C30 aromatic hydrocarbon substituted with a C1 toC20 alkyl group, a primary, secondary, a tertiary phosphine substitutedwith a C6 to C22 alkyl group, a primary, secondary, a tertiary phosphineoxide substituted with a C6 to C22 alkyl group, a C12 to C22 aromaticether, and a combination thereof.

The halogen source may include HF, NH₄F, HCl, NH₄Cl, HBr, NH₄Br, LiF,NaF, KF, BeF₂, MgF₂, CaF₂, SrF₂, CuF, AgF, AuF, ZnF₂, CdF₂, HgF₂, AlF₃,GaF₃, InF₃, SnF₂, PbF₂, LiCl, NaCl, KCl, BeCl₂, MgCl₂, CaCl₂, SrCl₂,CuCl, AgCl, AuCl, ZnCl₂, CdCl₂, HgCl₂, AlCl₃, GaCl₃, InCl₃, SnCl₂,PbCl₂, LiBr, NaBr, KBr, BeBr₂, MgBr₂, CaBr₂, SrBr₂, CuBr, AgBr, AuBr,ZnBr₂, CdBr₂, HgBr₂, AlBr₃, GaBr₃, InBr₃, SnBr₂, PbBr₂, LiI, NaI, KI,BeI₂, MgI₂, CaI₂, SrI₂, CuI, AgI, AuI, ZnI₂, CdI₂, HgI₂, AlI₃, GaI₃,InI₃, SnI₂, PbI₂, HBF₄, an ionic liquid including a halogen element, anda combination thereof.

The halogen source may be added in the first mixture in an amount ofgreater than or equal to about 0.5 mole percent, based on a total molesof the first metal of the first precursor.

The halogen source (e.g., HF) may be added as a solution in an carriersolvent, and the carrier solvent may include water, a ketone such asacetone, a primary amine, a secondary amine, a tertiary amine, aheterocyclic compound having a nitrogen atom such as pyridine, a C6 toC40 olefin, a C6 to C40 aliphatic hydrocarbon, a C6 to C30 aromatichydrocarbon substituted with a C1 to C20 alkyl group, a primary,secondary, or tertiary phosphine substituted with a C6 to C22 alkylgroup, a primary, secondary, or tertiary phosphine oxide substitutedwith a C6 to C22 alkyl group, a C7 to C40 aromatic ether, a C6 to C40aromatic alcohol, or a combination thereof.

In the solution, a molar concentration of the halogen source may begreater than or equal to about 0.001 moles per liter.

The heating the second mixture to the reaction temperature to trigger areaction between the first precursor and the second precursor may beconducted without irradiation with microwaves.

In another embodiment, a device may include the nanocrystal particle.

The device may be a light emitting diode (“LED”), an organic lightemitting diode (“OLED”), a sensor, an imaging sensor, a solar celldevice, or a liquid crystal display (“LCD”).

The foregoing method makes it possible to significantly enhance lightemitting properties of the semiconductor nanocrystal.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the embodiments, taken inconjunction with the accompanying drawings, in which:

FIG. 1 to FIGS. 3 each schematically illustrate an embodiment of adistribution of a halogen element, e.g., fluorine, in the semiconductornanoparticle;

FIG. 4 is a graph of intensity (arbitrary units, a.u.) versus wavelength(nanometers, nm) showing photoluminescence (“PL”) spectra of thenanocrystals prepared in Example 2-1 and Comparative Example 1,respectively;

FIG. 5 is a graph of intensity (arbitrary units, a.u.) versusdiffraction angle (degrees two-theta, 2θ) which includes X-raydiffraction (“XRD”) spectra of the nanocrystals prepared in Example 2-1and Comparative Example 1, respectively;

FIGS. 6A and 6B are each a graph of intensity (arbitrary units, a.u.)versus energy (electron volts, eV) showing the results of the XPSelement analysis of the nanocrystal prepared in Example 2-1;

FIGS. 7A and 7B show the results of the TEM-EDS analysis of thenanocrystal prepared in Example 2-1;

FIG. 7C is a graph of counts versus energy “kiloelectron volts, keV)showing the results of energy dispersive X-ray diffraction analysis ofthe nanocrystal prepared in Example 2-1;

FIG. 8 is a graph of intensity (a. u.) versus diffraction angle (2θ)showing the results of XRD analysis of the nanocrystal prepared inExample 5;

FIG. 9 is graph of intensity (a. u.) versus mass to charge ratio (m/z)showing the results of TOF-SIMS analysis of the nanocrystal of Example2-1;

FIG. 10 shows the results of the TEM analysis of the nanocrystal ofComparative Example 4;

FIG. 11 is a graph of counts versus energy “kiloelectron volts, keV)showing the results of energy dispersive X-ray diffraction analysis ofthe nanocrystal prepared in Comparative Example 4;

FIG. 12 is a graph of intensity (arbitrary units, a.u.) versuswavelength (nanometers, nm) showing photoluminescence (PL) spectra ofthe nanocrystal particles prepared in Example 9 and Reference Example 3;and

FIG. 13 is a graph of intensity (arbitrary units, a.u.) versuswavelength (nanometers, nm) showing photoluminescence (PL) spectra ofthe nanocrystal particles prepared in Comparative Example 7 andReference Example 3.

DETAILED DESCRIPTION

This disclosure will be described more fully hereinafter in thefollowing detailed description, in which some but not all embodiments ofthis disclosure are described. This disclosure may be embodied in manydifferent forms and is not be construed as limited to the embodimentsset forth herein; rather, these embodiments are provided so that thisdisclosure will fully convey the scope of the invention to those skilledin the art. Thus, in some exemplary embodiments, well known technologiesare not specifically explained. Unless otherwise defined, all terms usedin the specification (including technical and scientific terms) may beused with meanings commonly understood by a person having ordinaryknowledge in the art. Further, unless explicitly defined to thecontrary, the terms defined in a generally-used dictionary are notideally or excessively interpreted. In addition, unless explicitlydescribed to the contrary, the word “comprise” and variations such as“comprises” or “comprising” will be understood to imply the inclusion ofstated elements but not the exclusion of any other elements.

Unless specifically described to the contrary, a singular form includesa plural form.

As used herein, the term “quantum yield” and “light emitting efficiency”are equivalent and may be used interchangeably.

As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list.

It will be understood that, although the terms first, second, third,etc. may be used herein to describe various elements, components,regions, layers, and/or sections, these elements, components, regions,layers, and/or sections should not be limited by these terms. Theseterms are only used to distinguish one element, component, region,layer, or section from another element, component, region, layer, orsection. Thus, a first element, component, region, layer, or sectiondiscussed below could be termed a second element, component, region,layer, or section without departing from the teachings of the presentembodiments.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise. Unlessspecified otherwise, the term “or” means “and/or.”

As used herein, the term “nanocrystal particle” refers to a nano-sizedparticle including a crystalline material.

As used herein, the term “halogen element” has substantially the samemeaning as the term “halogen” and is not limited to an elementalhalogen. As used therein, the halogen element may constitute a halide.

As used herein, the term “Group II” may include Group IIA and Group IIB,and examples of the Group II metal includes Cd, Zn, Hg and Mg, but arenot limited thereto. As used herein, the term “Group III” may includeGroup IIIA and Group IIIB, and examples of the Group III metal include,but are not limited to, Al, In, Ga, and Tl.

As used herein, the term “Group IV” may include Group IVA and Group IVB,and examples of the Group IV metal may include, but are not limited to,Si, Ge, and Sn. As used herein, the term “metal” may also include ametalloid such as Si.

As used herein, Group I may include Group IA and Group IB, and examplesof the Group I metal may include, but are not limited to, Li, Na, K, Ru,Cs.

“Alkyl” as used herein means a straight or branched chain, saturated,monovalent hydrocarbon group (e.g., methyl or hexyl).

“Alkenyl” means a straight or branched chain, monovalent hydrocarbongroup having at least one carbon-carbon double bond (e.g., ethenyl(—HC═CH₂)).

“Aryl” means a monovalent group formed by the removal of one hydrogenatom from one or more rings of an arene (e.g., phenyl or napthyl).

“Aliphatic” means a saturated or unsaturated linear or branchedhydrocarbon group. An aliphatic group may be an alkyl, alkenyl, oralkynyl group, for example.

“Aromatic” means an organic compound or group comprising at least oneunsaturated cyclic group having delocalized pi electrons. The termencompasses both hydrocarbon aromatic compounds and heteroaromaticcompounds.

“Substituted” means that the compound or group is substituted with atleast one (e.g., 1, 2, 3, or 4) substituent independently selected froma hydroxyl (—OH), a C1-9 alkoxy, a C1-9 haloalkoxy, an oxo (═O), a nitro(—NO₂), a cyano (—CN), an amino (—NH₂), an azido (—N₃), an amidino(—C(═NH)NH₂), a hydrazino (—NHNH₂), a hydrazono (═N—NH₂), a carbonyl(—C(═O)—), a carbamoyl group (—C(O)NH₂), a sulfonyl (—S(═O)₂—), a thiol(—SH), a thiocyano (—SCN), a tosyl (CH₃C₆H₄SO₂—), a carboxylic acid(—C(═O)OH), a carboxylic C1 to C6 alkyl ester (—C(═O)OR wherein R is aC1 to C6 alkyl group), a carboxylic acid salt (—C(═O)OM) wherein M is anorganic or inorganic anion, a sulfonic acid (—SO₃H₂), a sulfonic mono-or dibasic salt (—SO₃MH or —SO₃M₂ wherein M is an organic or inorganicanion), a phosphoric acid (—PO₃H₂), a phosphoric acid mono- or dibasicsalt (—PO₃MH or —PO₃M₂ wherein M is an organic or inorganic anion), a C1to C12 alkyl, a C3 to C12 cycloalkyl, a C2 to C12 alkenyl, a C5 to C12cycloalkenyl, a C2 to C12 alkynyl, a C6 to C12 aryl, a C7 to C13arylalkylene, a C4 to C12 heterocycloalkyl, and a C3 to C12 heteroarylinstead of hydrogen, provided that the substituted atom’s normal valenceis not exceeded.

In an embodiment, a nanocrystal particle may include at least onesemiconductor material and at least one halogen element. The nanocrystalparticle may have a ligand compound coordinating a surface thereof. Thehalogen element may be selected from fluorine (F), chlorine (Cl),bromine (Br), iodine (I), and a combination thereof. The halogen may befluorine (F). The nanocrystal particle may have a core including a firstnanocrystal, and a shell on, e.g., surrounding, the core, the shellincluding a crystalline or amorphous material. As used herein, “theshell surrounding the core” includes the case where the shell at leastpartially (or completely) surrounds the core. The shell may be amulti-layered shell having at least two layers, each of the layersincluding the same or different crystalline or amorphous materials. Thecore may include a first semiconductor material. The crystallinematerial of the shell may be a second semiconductor material that isdeposited on the core and that is different from the first semiconductormaterial.

The first semiconductor nanocrystal may of the core include a metalselected from a Group II metal, a Group III metal, a Group IV metal, anda combination thereof, and the crystalline or amorphous material of theshell may include a second metal that is different from the first metal.The second metal may be included in the first semiconductor nanocrystaland is selected from a Group I metal, a Group II metal, a Group IIImetal, a Group IV metal, and a combination thereof.

The halogen 10 (e.g., fluorine) may be included in the nanocrystalparticle 11 (e.g., a semiconductor nanocrystal particle), for examplemay be inside the particle (see FIG. 1 ). For example, the semiconductornanocrystal particle having a core-shell structure includes the halogen(e.g., fluorine) inside the core. The halogen may be present at aninterface between the core 13 and the shell 14 (see FIG. 2 ). In thenanocrystal particle, the presence of the halogen element at theinterface between the core and the shell may be confirmed by the factthat the analysis of the nanocrystal particle detects a halogen compound(e.g., halide) including the halogen element and the core metal and ahalogen compound (e.g., halide) including the halogen element and theshell metal at the same time. Without wishing to be bound by any theory,such a result may suggest that the halogen element may be present at theinterface between the core and the shell (e.g., a thin interlayer or athin interdiffusion region formed between the core and the shell). Thehalogen 10 may be present in the shell (see FIG. 3 ). When thesemiconductor nanocrystal particle has a multi-shell structure, thehalogen may be present in the inner shell (i.e., an inner layer of theshell), in the outer shell (i.e., an outer layer of the shell being onthe inner layer), or both, wherein the inner shell is between the coreand the outer shell. The halogen may be included in an amount of greaterthan or equal to about 0.05 mole percent, based on a total molar amountof a metal component of the core of the nanocrystal. The nanocrystalparticle may have a ligand compound 12 coordinating a surface thereof,but it is not limited thereto

The presence of the halogen element included in the nanoparticle (e.g.,a semiconductor nanocrystal) may be determined in various manners suchas X-ray photoelectron spectroscopy (“XPS”), energy dispersivespectroscopy (“EDS”), a time-of-flight secondary ion mass spectrometry(“TOF-SIMS”), and the like. The halogen may be present in thenanoparticle by being doped therein. The halogen may be present in theform of a metal halide such as a metal fluoride. The metal halide may beselected from a halide including a Group I metal, a halide including aGroup II metal, a halide including a Group III metal, and a combinationthereof. The halogen element may be substituted into a crystallinestructure of the particle or may be introduced as an interstitial atomin the crystalline structure thereof. The halogen element may be in thecore, at the interface between the core and the shell, and/or in theshell. In an embodiment, the shell may comprise, or may be a shellconsisting of, a metal halide (e.g., a metal fluoride). The metal halidemay include a compound selected from LiF, NaF, KF, BeF₂, MgF₂, CaF₂,SrF₂, CuF, AgF, AuF, ZnF₂, CdF₂, HgF₂, AlF₃, GaF₃, InF₃, SnF₂, PbF₂,LiCl, NaCl, KCl, BeCl₂, MgCl₂, CaCl₂, SrCl₂, CuCl, AgCl, AuCl, ZnCl₂,CdCl₂, HgCl₂, AlCl₃, GaCl₃, InCl₃, SnCl₂, PbCl₂, LiBr, NaBr, KBr, BeBr₂,MgBr₂, CaBr₂, SrBr₂, CuBr, AgBr, AuBr, ZnBr₂, CdBr₂, HgBr₂, AlBr₃,GaBr₃, InBr₃, SnBr₂, PbBr₂, LiI, NaI, KI, BeI₂, MgI₂, CaI₂, SrI₂, CuI,AgI, AuI, ZnI₂, CdI₂, HgI₂, AlI₃, GaI₃, InI₃, SnI₂, PbI₂, and acombination thereof.

A nanocrystal particle including a semiconductor material (as usedherein, it may also be referred to as a semiconductor nanocrystalparticle) may have an energy bandgap selected based on the size and thecomposition thereof, and has high color purity in terms of lightemitting properties. Therefore, it has attracted a lot of attention as amaterial that may be utilized in various fields such as a display, theenergy industry, the semiconductor industry, and biology relatedapplications. However, most types of the semiconductor nanocrystalparticles showing satisfactory properties include cadmium (Cd). Cadmiumis one of elements posing serious environmental threats and thus it isurgently desired to develop a cadmium-free semiconductor nanocrystalparticle having excellent light-emitting properties. For instance, aGroup III-V nanocrystal is an example of a Cd-free semiconductornanocrystal, but its synthesis process uses a precursor that is far moresusceptible to oxidation than a synthesis process for a Cd-basedsemiconductor nanocrystal (e.g., a CdSe-based quantum dot) and theprecursor thereof has poor reactivity, making the control of thereaction much more difficult. The InP/ZnS core-shell semiconductornanocrystal is an extensively researched Group III-V quantum dots.However, the InP based semiconductor nanocrystals generally tend toexhibit lower light emitting efficiency and poor light emittingproperties. In addition, a size of the particle that is used to emit adesired wavelength of light ranges from 2 nanometers (nm) to 5 nm, andthus the synthesis of the InP-based nanocrystal is not easy. Also, thelight emitting properties of the Cd-free quantum dots such as the InPnanocrystal are lower than those of the CdSe based quantum dots.

In contrast, in accordance with the aforementioned embodiments, thesemiconductor nanocrystal may have significantly enhanced light emittingproperties by introducing a halogen element into the semiconductornanocrystal even when it does not include cadmium. In this regard, therewas an attempt to increase light emitting efficiency by treating thesemiconductor nanocrystal with hydrofluoric acid and thereby removing anoxide or a dangling bond from a surface of the nanocrystal particle (seeS. Adam et al., J. Chem. Phys. 123, 084706, 2005, which is incorporatedherein by reference in its entirety). However, the enhancementattainable by the hydrofluoric acid treatment is limited. There wasanother attempt to treat a surface of an InP nanocrystal before shellingthereon, and it was confirmed that such shelling is very difficult toproduce (see J. Mater. Chem., 18, 2653, 2008, which is incorporatedherein by reference). Also, a Cd-free semiconductor nanocrystal is oftenprepared to have a core-shell structure. For example, it is oftendesired to shell other semiconductor materials such as ZnSe, ZnS, CdS,and the like on the Group III-V core (e.g., an InP core), but it isquite difficult to form a shell on a core with other semiconductormaterials and thus enhancing light emitting properties by introducing acore-shell structure may become more difficult (see Comparative Example4). For example, quantum efficiency of an InP core-shell semiconductornanocrystal may be normally at most about 40 %.

By contrast, the aforementioned semiconductor nanocrystal may showgreatly improved light-emitting properties (e.g., high quantumefficiency and narrow full width at half maximum) by introducing ahalogen element into the semiconductor nanocrystal particle having acore-shell structure (for example, in the core, in the shell, and/or atan interface therebetween). In particular, the aforementionedsemiconductor nanocrystal may have a quantum yield that is comparable orhigher than that of the Cd-based semiconductor nanocrystal even when itdoes not include the cadmium.

The ligand compound may be any suitable ligand compound known in the artwithout particular limitation. For example, the ligand compound mayinclude a compound represented by RCOOH, RNH₂, R₂NH, R₃N, RSH, R₃PO,R₃P, ROH, RCOOR′, RPO(OH)₂, R₂POOH, or a combination thereof, wherein Rand R′ are independently a C1 to C24 alkyl group, a C2 to C24 alkenylgroup, and a C6 to C20 aryl group. The organic ligand compound maycoordinate the surface of the nanocrystals as prepared, playing a roleof well-dispersing the nanocrystals in a solution, and it may have aneffect on the light-emitting and electrical characteristics of thenanocrystals. Examples of the organic ligand compound may include, butare not limited to, methanethiol, ethanethiol, propanethiol,butanethiol, pentanethiol, hexanethiol, octanethiol, dodecanethiol,hexadecanethiol, octadecanethiol, benzylthiol, methaneamine,ethaneamine, propaneamine, butaneamine, pentaneamine, hexaneamine,octaneamine, dodecaneamine, hexadecylamine, octadecylamine,dimethylamine, diethylamine, dipropylamine, methanoic acid, ethanoicacid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid,heptanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid,octadecanoic acid, oleic acid, benzoic acid, a phosphine such asmethylphosphine, ethylphosphine, propylphosphine, butylphosphine,pentylphosphine, and the like, a phosphine oxide compound such asmethylphosphine oxide, ethylphosphine oxide, propylphosphine oxide,butylphosphine oxide, and the like, a diphenylphosphine compound, atriphenylphosphine compound, an oxide compound thereof, and the like,and a phosphonic acid, and a combination thereof. The organic ligandcompound may be used alone or as a mixture of two or more compounds.

The first nanocrystal (or the first semiconductor material) may includea Group II-VI compound, a Group III-V compound, a Group IV-VI compound,a Group IV compound, or a combination thereof.

The crystalline material (or the second semiconductor material) or theamorphous material may have a different composition from the firstnanocrystal (or the first semiconductor material), and may include aGroup II-VI compound, a Group III-V compound, a Group IV-VI compound, aGroup IV compound, a halogen compound containing a metal (for example, ahalide selected from LiF, NaF, KF, BeF₂, MgF₂, CaF₂, SrF₂, CuF, AgF,AuF, ZnF₂, CdF₂, HgF₂, AlF₃, GaF₃, InF₃, SnF₂, PbF₂, LiCl, NaCl, KCl,BeCl₂, MgCl₂, CaCl₂, SrCl₂, CuCl, AgCl, AuCl, ZnCl₂, CdCl₂, HgCl₂,AlCl₃, GaCl₃, InCl₃, SnCl₂, PbCl₂, LiBr, NaBr, KBr, BeBr₂, MgBr₂, CaBr₂,SrBr₂, CuBr, AgBr, AuBr, ZnBr₂, CdBr₂, HgBr₂, AlBr₃, GaBr₃, InBr₃,SnBr₂, PbBr₂, LiI, NaI, KI, BeI₂, MgI₂, CaI₂, SrI₂, CuI, AgI, AuI, ZnI₂,CdI₂, HgI₂, AlI₃, GaI₃, InI₃, SnI₂, PbI₂, and a combination thereof), ametal oxide, ora combination thereof.

The Group II-VI compound may be selected from:

-   a binary element compound selected from CdSe, CdTe, ZnS, ZnSe, ZnTe,    ZnO, HgS, HgSe, HgTe, MgSe, MgS, and a combination thereof;-   a ternary element compound selected from CdSeS, CdSeTe, CdSTe,    ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe,    CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, and a    combination thereof; and-   a quaternary element compound selected from HgZnTeS, CdZnSeS,    CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe,    HgZnSTe, and a combination thereof.

The Group III-V compound may be selected from:

-   a binary element compound selected from GaN, GaP, GaAs, GaSb, AlN,    AlP, AlAs, AlSb, InN, InP, InAs, InSb, and a combination thereof;-   a ternary element compound selected from GaNP, GaNAs, GaNSb, GaPAs,    GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs,    InPSb, and a combination thereof; and-   a quaternary element compound selected from GaAlNP, GaAlNAs,    GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs,    GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and a    combination thereof.

The Group IV-VI compound may be selected from:

-   a binary element compound selected from SnS, SnSe, SnTe, PbS, PbSe,    PbTe, and a combination thereof;-   a ternary element compound selected from SnSeS, SnSeTe, SnSTe,    PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and a combination    thereof; and-   a quaternary element compound selected from SnPbSSe, SnPbSeTe,    SnPbSTe, and a combination thereof.

The Group IV compound may be a singular element selected from:

-   Si, Ge, and a combination thereof; and-   a binary element compound selected from SiC, SiGe, and a combination    thereof.

The semiconductor nanocrystal may absorb light of a wavelength of about300 nm to about 700 nm and emit light of a wavelength from about 400 nmto about 600 nm, from about 600 nm to about 700 nm, or from about 550 nmto about 650 nm. The wavelength of the emitted light may be easilyadjusted by controlling the composition and the size of thesemiconductor nanocrystal.

The semiconductor nanocrystal may have a quantum yield of about 30 % toabout 100 %, for example, greater than or equal to about 50 %, greaterthan or equal to about 60 %, greater than or equal to about 70 %,greater than or equal to about 80 %, or greater than or equal to about90 %. If desired, the semiconductor nanocrystal may have a wider ornarrower full width at half maximum (“FWHM”) in its photoluminescencespectrum. For example, in order to be used in a display, thesemiconductor nanocrystal may have a narrow FWHM to realize enhancedcolor purity or color reproducibility. In this case, the semiconductornanocrystal may have a FWHM of less than or equal to about 50 nm, forexample, less than or equal to about 40 nm in its photoluminescencespectrum.

The semiconductor nanocrystal particle may have a particle diameter (thelongest diameter in case of a non-spherical particle) ranging from about1 nm to about 100 nm, for example about 1 nm to about 20 nm.

The shape of the nanocrystal particle, e.g., the semiconductornanocrystal, is not particularly limited. By way of an example, thenanoparticle may have a spherical shape, a pyramidal shape, a multi-armshape, or a cubic shape. The nanocrystal may be in the form of ananosphere, a nanotube, a nanowire, a nano-fiber, a nano-plate, or thelike.

In another embodiment, a process of synthesizing a nanoparticleincludes:

-   obtaining a first mixture including a first precursor, a ligand    compound, and a solvent;-   optionally heating the first mixture;-   contacting a source of an halogen element, a second precursor, and    optionally a first nanocrystal with the first mixture, which is    optionally heated, to obtain a second mixture; and-   heating the second mixture to a reaction temperature to react the    first precursor and the second precursor to obtain a nanocrystal    particle including at least one semiconductor material and the    halogen element.

The first precursor may include a plurality compounds. The secondprecursor may include a plurality compounds. When the plurality ofcompounds is used for the first or second precursor, they may be addedat the same time or with a time lag therebetween to the first mixture(optionally heated) either at the same temperature or at differenttemperatures. In case of the first precursor, a mixture including anadditional precursor compound, a ligand, and a solvent is first preparedand then added to the first mixture already prepared.

The first precursor may include a metal selected from Group II metal, aGroup III metal or a Group IV metal, and a combination thereof, and Thefirst precursor may be in a form selected from an elemental metal (e.g.,a metal powder), an alkylated metal compound, a metal alkoxide, a metalcarboxylate, a metal nitrate, a metal perchlorate, a metal sulfate, ametal acetylacetonate, a metal halide, a metal cyanide, a metalhydroxide, a metal oxide, a metal peroxide, and a combination thereof.Examples of the first precursor may include, but are not limited to,dimethyl zinc, diethyl zinc, zinc acetate, zinc acetylacetonate, zinciodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinccyanide, zinc nitrate, a zinc oxide, zinc peroxide, zinc perchlorate,zinc sulfate, zinc stearate, dimethyl cadmium, diethyl cadmium, cadmiumacetate, cadmium acetylacetonate, cadmium iodide, cadmium bromide,cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate,cadmium oxide, cadmium perchlorate, cadmium phosphide, cadmium sulfate,mercury acetate, mercury iodide, mercury bromide, mercury chloride,mercury fluoride, mercury cyanide, mercury nitrate, mercury oxide,mercury perchlorate, mercury sulfate, lead acetate, lead bromide, leadchloride, lead fluoride, lead oxide, lead perchlorate, lead nitrate,lead sulfate, lead carbonate, tin acetate, tin bis(acetylacetonate), tinbromide, tin chloride, tin fluoride, tin oxide, tin sulfate, germaniumtetrachloride, germanium oxide, germanium ethoxide, trimethyl gallium,triethyl gallium, gallium acetylacetonate, gallium- chloride, galliumfluoride, gallium oxide, gallium nitrate, gallium sulfate, trimethylindium, indium acetate, indium hydroxide, indium chloride, indium oxide,indium nitrate, indium sulfate, thallium acetate, thalliumacetylacetonate, thallium chloride, thallium oxide, thallium ethoxide,thallium nitrate, thallium sulfate, and thallium carbonate. The firstprecursor may be used alone or in a combination thereof depending on thecomposition of the nanocrystal intended to be synthesized.

The second precursor may be appropriately selected depending on the typeof the nanocrystal intended to be synthesized. In a non-limitingexample, the second precursor may be a compound including a Group Velement or a Group VI element. In another example, the second precursormay be a compound including a halogen (e.g., HF). In some examples, thehalogen source and the second precursor may be the same compound.Non-limiting examples of the second precursor may include, but are notlimited to, hexanethiol, octanethiol, decanethiol, dodecanethiol,hexadecanethiol, mercaptopropylsilane, sulfur-trioctylphosphine(“S-TOP”), sulfur-tributylphosphine (“S-TBP”), sulfur-triphenylphosphine(“S-TPP”), sulfur-trioctylamine (“S-TOA”), bistrimethylsilyl sulfide,ammonium sulfide, sodium sulfide, selenium-trioctylphosphine (“Se-TOP”),selenium-tributylphosphine (“Se-TBP”), selenium-triphenylphosphine(“Se-TPP”), tellurium-tributylphosphine (“Te-TBP”),tellurium-triphenylphosphine (“Te-TPP”), tris(trimethylsilyl)phosphine,tris(dimethylamino)phosphine, triethylphosphine, tributylphosphine,trioctylphosphine, triphenylphosphine, tricyclohexylphosphine, arsenicoxide, arsenic chloride, arsenic sulfate, arsenic bromide, arseniciodide, nitric oxide, nitric acid, ammonium nitrate, HF, NH₄F, HCl,NH₄Cl, HBr, NH₄Br, LiF, NaF, KF, BeF₂, MgF₂, CaF₂, SrF₂, CuF, AgF, AuF,ZnF₂, CdF₂, HgF₂, AlF₃, GaF₃, InF₃, SnF₂, PbF₂, LiCl, NaCl, KCl, BeCl₂,MgCl₂, CaCl₂, SrCl₂, CuCl, AgCl, AuCl, ZnCl₂, CdCl₂, HgCl₂, AlCl₃,GaCl₃, InCl₃, SnCl₂, PbCl₂, LiBr, NaBr, KBr, BeBr₂, MgBr₂, CaBr₂, SrBr₂,CuBr, AgBr, AuBr, ZnBr₂, CdBr₂, HgBr₂, AlBr₃, GaBr₃, InBr₃, SnBr₂,PbBr₂, LiI, NaI, KI, BeI₂, MgI₂, CaI₂, SrI₂, CuI, AgI, AuI, ZnI₂, CdI₂,HgI₂, AlI₃, GaI₃, InI₃, SnI₂, PbI₂, and an ionic liquid including ahalogen (e.g., fluorine). The second precursor may be used alone or in acombination thereof depending on the composition of the nanocrystalintended to be synthesized.

The ligand compound is the same as set forth above.

The solvent may be selected from a C6 to C22 primary amine such ashexadecyl amine; a C6 to C22 secondary amine such as dioctyl amine; a C6to C40 tertiary amine such as trioctyl amine; a heterocyclic compoundhaving a nitrogen atom such as pyridine; a C6 to C40 aliphatichydrocarbon (e.g., an alkane, an alkene, or an alkyne) such ashexadecane, octadecane, octadecene, squalane, and the like; a C6 to C30aromatic hydrocarbon such as phenyl dodecane, phenyl tetradecane, phenylhexadecane, and the like; a phosphine substituted with a C6 to C22 alkylgroup such as trioctyl phosphine; a phosphine oxide substituted with aC6 to C22 alkyl group such as trioctyl phosphine oxide; a C12 to C22aromatic ether such as phenyl ether, benzyl ether, and the like; and acombination thereof.

In the first mixture, the amount of the first precursor, the ligandcompound, and the solvent may be selected appropriately without anyparticular limitations.

The optional heating of the first mixture may be carried out by heatingthe first mixture under vacuum at a temperature of greater than or equalto about 40° C., for example, greater than or equal to about 50° C.,greater than or equal to about 60° C., greater than or equal to about70° C., greater than or equal to about 80° C., greater than or equal toabout 90° C., greater than or equal to about 100° C., or greater than orequal to about 120° C., and/or heating the same under a nitrogenatmosphere at a temperature of greater than or equal to about 100° C.,for example, greater than or equal to about 150° C., greater than orequal to about 180° C., or greater than or equal to about 200° C., orabout 40° C. to about 250° C.

A halogen source and a second precursor are added to the first mixture(as optionally heated) to obtain a second mixture. In an embodiment, themethod may further include adding a first nanocrystal to the (optionallyheated) first mixture, and thereby the final nanocrystal particle mayhave a core-shell structure wherein a nanocrystal formed by the reactionbetween the first and second precursors is deposited on the surface ofthe first nanocrystal particle (i.e., the core). When the firstnanocrystal has a core-shell structure, the final nanocrystal may have acore-multishell structure, and the halogen element may be present at anouter shell.

In the second mixture, the amounts of the halogen source, the secondprecursor, and the first nanocrystal optionally being added are notparticularly limited, and may be selected depending on the nanocrystalstructure intended to be obtained.

The halogen source, the second precursor, and optionally the firstnanocrystal may be added simultaneously or sequentially. For example,when the halogen source, the second precursor, and optionally the firstnanocrystal are added sequentially, the sequence therebetween is notparticularly limited. In other words, the halogen source, the secondprecursor, and optionally the first nanocrystal are added in any order.When the halogen source, the second precursor, and optionally the firstnanocrystal are added, the aforementioned solvent and the like may beused together.

The halogen source may include HF, NH₄F, HCl, NH₄Cl, HBr, NH₄Br LiF,NaF, KF, BeF₂, MgF₂, CaF₂, SrF₂, CuF, AgF, AuF, ZnF₂, CdF₂, HgF₂, AlF₃,GaF₃, InF₃, SnF₂, PbF₂, LiCl, NaCl, KCl, BeCl₂, MgCl₂, CaCl₂, SrCl₂,CuCl, AgCl, AuCl, ZnCl₂, CdCl₂, HgCl₂, AlCl₃, GaCl₃, InCl₃, SnCl₂,PbCl₂, LiBr, NaBr, KBr, BeBr₂, MgBr₂, CaBr₂, SrBr₂, CuBr, AgBr, AuBr,ZnBr₂, CdBr₂, HgBr₂, AlBr₃, GaBr₃, InBr₃, SnBr₂, PbBr₂, LiI, NaI, KI,BeI₂, MgI₂, CaI₂, SrI₂, CuI, AgI, AuI, ZnI₂, CdI₂, HgI₂, AlI₃, GaI₃,InI₃, SnI₂, PbI₂, an ionic liquid containing a halogen element (e.g.,fluorine), or a combination thereof.

The halogen source may be used together with a solvent for example, aheterocyclic compound containing nitrogen such as pyridine, H₂O, a C3 toC12 ketone such as acetone, methyl ethyl ketone, and the like, a C1 toC40 primary, secondary, tertiary amine such as trioctylamine, or acombination thereof. In an embodiment, the halogen source (e.g., HF) maybe dissolved in a carrier solvent to be prepared as a solution, which isthen added to the first mixture. The carrier solvent may be water, aheterocyclic compound containing nitrogen such as pyridine, a C3 to C12ketone such as acetone, methyl ethyl ketone, a primary amine for examplehaving 1 to 40 carbon atoms, a primary alcohol for example having 1 to40 carbon atoms, a secondary amine for example having 2 to 40 carbonatoms, a secondary alcohol for example having 2 to 40 carbon atoms, atertiary amine for example having 3 to 40 carbon atoms, a tertiaryalcohol for example having 3 to 40 carbon atoms, a heterocyclic compoundhaving nitrogen, an olefin, an aliphatic hydrocarbon, an aromatichydrocarbon having an alkyl substituent, a phosphine having an alkylsubstituent, a phosphine oxide having an alkyl substituent, an aromaticether, or a combination thereof. In the solution dissolved in thecarrier solvent, a molar concentration of the halogen source may begreater than or equal to about 0.001 mol/L.

The ionic liquid is a salt in a liquid state and it consists of an ionand a counter ion thereof. In an embodiment, the ionic liquid may be asubstituted or unsubstituted imidazolium salt, a substituted orunsubstituted pyrazolium salt, a substituted or unsubstituted triazoliumsalt, a substituted or unsubstituted thiazolium salt, a substituted orunsubstituted oxazolium salt, a substituted or unsubstitutedpyridazinium salt, a substituted or unsubstituted pyrimidinium salt, asubstituted or unsubstituted ammonium salt, a substituted orunsubstituted phosphonium salt, a substituted or unsubstituted sulfoniumsalt, a substituted or unsubstituted pyridinium salt, a substituted orunsubstituted pyrrolidinium salt, or a combination thereof. The ionicliquid may have a halide anion such as F⁻, a tetrafluoroborate anion(BF₄ ⁻), a hexafluorophosphate anion (PF₆ ⁻), a perchlorate anion (ClO₄⁻ ), an acetate anion, a trifluoroacetate anion, a triflate anion, ahydrogen sulfate anion, an alkyl sulfate anion, a sulphite anion, ahydrogen sulphite anion, a chloroaluminate anion, a tetrabromoaluminateanion, a nitrite anion, a nitrate anion, a dichlorocuprate anion, aphosphate anion, a hydrogen phosphate anion, a dihydrogen phosphateanion, a carbonate anion, a hydrogen carbonate anion, a sulfonate anion,a tosylate anion, or a bis(trifluoromethyl sulphonyl)imide anion. In anembodiment, the ionic liquid may be an imidazolium salt, a pyridiniumsalt, a phosphonium salt, or an ammonium salt, and it may have F⁻, BF₄⁻, or PF₆ ⁻ as an anion. The ionic liquid may be used alone or in acombination thereof.

The halogen source may be added to the first mixture in an amount ofgreater than or equal to about 0.5 %, for example greater than or equalto about 5%, or greater than or equal to about 10 % based on the amount(mole) of the first metal precursor.

The heating the second mixture to the reaction temperature to trigger areaction between the first precursor and the second precursor may beconducted without irradiation with microwaves.

The reaction temperature is not particularly limited and may be selectedproperly in light of the types of the first precursor, the secondprecursor, the halogen source, the solvent as used, and the like. Forexample, the reaction temperature may be about 100° C. to 350° C., forexample, about 220° C. to 320° C.

The first semiconductor nanocrystal may include a Group II-VI compound,a Group III-V compound, a Group IV-VI compound, a Group IV compound, ora combination thereof. In an embodiment, the first nanocrystal mayinclude a Group III-V compound.

The nanocrystal formed by the reaction between the first precursor andthe second precursor may include at least one compound selected from aGroup II-VI compound, a Group III-V compound, a Group IV-VI compound, aGroup IV compound, LiF, NaF, KF, BeF₂, MgF₂, CaF₂, SrF₂, CuF, AgF, AuF,ZnF₂, CdF₂, HgF₂, AlF₃, GaF₃, InF₃, SnF₂, PbF₂, LiCl, NaCl, KCl, BeCl₂,MgCl₂, CaCl₂, SrCl₂, CuCl, AgCl, AuCl, ZnCl₂, CdCl₂, HgCl₂, AlCl₃,GaCl₃, InCl₃, SnCl₂, PbCl₂, LiBr, NaBr, KBr, BeBr₂, MgBr₂, CaBr₂, SrBr₂,CuBr, AgBr, AuBr, ZnBr₂, CdBr₂, HgBr₂, AlBr₃, GaBr₃, InBr₃, SnBr₂,PbBr₂, LiI, NaI, KI, BeI₂, MgI₂, CaI₂, SrI₂, CuI, AgI, AuI, ZnI₂, CdI₂,HgI₂, AlI₃, GaI₃, InI₃, SnI₂, PbI₂, and a combination thereof.

The Group II-VI compound, the Group III-V compound, and the Group IV-VIcompound are the same as set forth above. When the semiconductornanocrystal includes at least two kinds of compounds or when it is abinary element compound, a ternary element compound, or a quaternaryelement compound, it may be present in a form of an alloy, or in a formof a structure wherein at least two different crystalline structurescoexist as layers such as a core/shell or as compartments such asmulti-pods.

The aforementioned method of synthesizing a nanocrystal particle mayfurther include: adding a non-solvent to the reaction product betweenthe first and second precursors to separate a nanocrystal particle, towhich the ligand compound is coordinated. The non-solvent may be a polarsolvent that may be mixed with the solvent used during the reaction, butis not capable of dispersing nanocrystals. The non-solvent may beselected depending on the types of the solvent being used in thereaction. For example, the non-solvent may be selected from acetone,ethanol, butanol, isopropanol, water, tetrahydrofuran (“THF”), dimethylsulfoxide (“DMSO”), diethylether, formaldehyde, acetaldehyde, ethyleneglycol, a solvent having a similar solubility parameter to the foregoingsolvent, and a combination thereof. The separation may be performedusing centrifugation, precipitation, chromatography, or distillation.The separated nanocrystals may be added into a washing solvent asneeded. The washing solvent is not particularly limited, and may be asolvent having a similar solubility parameter to the ligand, such ashexane, heptane, octane, chloroform, toluene, benzene, and the like.

The nanocrystal prepared in accordance with the aforementioned processmay exhibit a high level of quantum yield. The semiconductor nanocrystalcompositions may find their utility in various fields such as a lightemitting diode (“LED”), a solar cell, a biosensor, or image sensor.According to the aforementioned method, it is possible to obtain asemiconductor nanocrystal particle having enhanced light emittingproperties.

Hereinafter, the present invention is illustrated in more detail withreference to specific examples. However, they are exemplary embodimentsof the present invention, and the present invention is not limitedthereto.

EXAMPLES Example I Reference Example 1: Preparation of InP Core

0.2 mmol of indium acetate, 0.6 mmol of palmitic acid, and 10 mL of1-octadecene are placed in a flask, subjected to a vacuum state at 120°C. for one hour, and then heated to 280° C. after the atmosphere in theflask is exchanged with N₂. Then, a mixed solution of 0.1 mmol oftris(trimethylsilyl)phosphine (“TMS3P”) and 0.5 mL of trioctylphosphine(“TOP”) is quickly injected and the reaction proceeds for 20 minutes.The reaction mixture then is rapidly cooled and acetone is added theretoto produce nanocrystals, which are then separated by centrifugation anddispersed in toluene. UV first absorption maximum of the InP corenanocrystals thus prepared is 420~600 nm.

Example 1: Preparation of InP(F) Nanocrystal

As used therein, the term “composition of the compound (halogen atom)”(e.g., “InP(F)”) refers to the case where the halogen atom (e.g.,fluorine) is included in the semiconductor nanocrystal particle of acertain composition (e.g., InP) in any manner (for example, as a dopedelement, as a metal halide (InF), and/or being substituted into acrystalline structure or being introduced as an interstitial atom.

0.2 mmol of indium acetate, 0.6 mmol of palmitic acid, and 10 mL of1-octadecene are placed in a flask, subjected to a vacuum state at 120°C. for one hour, and then heated to 280° C. after the atmosphere in theflask is exchanged with N₂. A solution of a mixture of 0.07 mmol of HFand 1.5 mL of trioctyl amine is quickly injected thereto and then amixed solution of 0.1 mmol of tris(trimethylsilyl)phosphine (“TMS3P”)and 0.5 mL of trioctylphosphine (“TOP”) is quickly injected. Thereaction proceeds for 20 minutes. The reaction mixture is then rapidlycooled to room temperature and acetone is added thereto to producenanocrystals, which are then separated by centrifugation and dispersedin toluene.

Example II Example 2-1: Preparation of an InP/ZnS(F) NanocrystalParticle

1.2 mmoL (0.224 g) of zinc acetate, 2.4 mmol (0.757 g) of oleic acid,and 10 mL of trioctylamine are placed in a flask, subjected to a vacuumstate at 120° C. for 10 minutes, and then heated to 280° C. after theatmosphere in the flask is exchanged with N₂. A toluene dispersion ofthe InP semiconductor nanocrystal prepared in Reference Example 1 (OD=optical density of 1^(st) excitonic absorption, OD:0.15, or 1 ml of a 1wt% toluene solution) is added thereto within 10 seconds, and then 1.5mL of a mixed solution including 0.14 mmol of HF (6 microliters (µL) ofan aqueous solution) in trioctylamine (TOA, a carrier solvent) isquickly injected, immediately after which 2.4 mmol of S/TOP is addedthereto and the reaction proceeds for 120 minutes. After that, thereaction mixture is rapidly cooled to room temperature and acetone isadded thereto to produce nanocrystal particles, which are then separatedby centrifugation and dispersed again in toluene.

Example 2-2:

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that HF is used in an amount of 0.07 mmolinstead of 0.14 mmol.

Example 2-3:

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that HF is used in an amount of 0.2 mmolinstead of 0.14 mmol.

Example 2-4:

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that HF is used in an amount of 0.4 mmolinstead of 0.14 mmol.

Example 2-5:

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that instead of HF, pyridine-HF is used asa fluorine source.

Example 2-6:

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that instead of HF, NH₄F is used as afluorine source.

Example 2-7:

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that instead of HF, ZnF₂ is used as afluorine source.

Example 2-8:

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that instead of HF, an ionic liquid,1-Butyl-3-methylimidazolium tetrafluoroborate is used as a fluorinesource.

Examples 2-9 to 2-11

Quantum yield depending on the introduction sequence of the firstnanocrystal, the source of the fluorine element, and the secondprecursor

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that (1) an InP core, (2) an HF/TOAsolution, and (3) 0.6 mmol of S/TOP are introduced according to thesequence set forth in Table 1.

TABLE 1 Example 2-1 Example 2-9 Example 2-10 Example 2-11 Introductionsequence (1) → (2) → (3) (1) →5 min.→ (2) → (3) ((1)+(2) 5 min. mixing )→ (3) (1) → (3) → 5 min. → (2)

Example 2-12:

InP/ZnS(F) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that 1.5 mL of a mixed solution including0.14 mmol HF (aqueous solution 6 µL)/ acetone (a carrier solvent) isused instead of a mixed solution of HF/TOA.

Comparative Example 1: Preparation of InP/ZnS Nanocrystal

An InP/ZnS nanocrystal particle is prepared in the same manner as setforth in Example 2-1, except that the mixed solution including 0.14 mmolof HF (6 µL of an aqueous solution) in trioctylamine (TOA, a carriersolvent) is not used.

Evaluation II

The structures of the nanocrystals of Example 2-1 and ComparativeExample 1 are determined.

An X-ray diffraction analysis is made for the nanocrystal particlesprepared above using Philips XPert PRO at a power of 3 kW to find outthe crystalline structure of InP/ZnS. The results are shown in FIG. 5 .FIG. 5 confirms that the nanocrystals of Example 2-1 and ComparativeExample 1 have a crystalline structure of InP/ZnS.

An X-ray photoelectron spectroscopy elemental analysis is made for thenanocrystal particles prepared using Quantum 2000 of PhysicalElectronics under the following conditions: 0.5~15 keV, 300 W, minimumanalysis region: 10 micro, sputter rate: 0.1 nm/min. The results areshown in Table 2 and FIG. 6A and FIG. 6B. The results of Table 2 confirmthat the particles have fluorine thereinside. The upward shift of Zn 2Pbinding energy may confirm the Zn—F bonding. The results confirm thatthe nanocrystal particle of Comparative Example 1 does not have fluorinetherein.

TABLE 2 XPS analysis (mole ratio) F P S Zn In F/Zn F/In InP (ReferenceExample 1) 0 2.83 0.00 0.00 5.77 - - InP/ZnS (Comparative Example 1) 02.2 3.75 5.98 2.99 0.00 InP/ZnS(F) (Example 2-1) 0.12 2.18 0.75 2.001.40 0.06 0.08

In addition, a transmission electronic microscopy - electron dispersivespectroscopy (TEM-EDS) analysis is made to prove the presence offluorine in the nanocrystal particle of Example 2-1 and the synthesis ofInP/ZnS(F). The results are shown in FIG. 7A, FIG. 7B, and FIG. 7C. TheTEM results of FIG. 7 confirm that an InP/ZnS(F) nanocrystal particle assynthesized has a size of about 2 to 5 nm. The EDS results of FIGS. 7Ato 7C confirm that fluorine is present inside the nanocrystal particle.

For the nanocrystals of Example 2-1 and Comparative Example 1, ATime-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) analysis ismade using TOF-SIMS V (ION-TOF GmbH, Germany) equipped with a 25 keV Bi+ion gun, and the result are shown in Table 3 and FIG. 9 .

For TOF-SIMS imaging, the ion gun is operated at 5 kHz with a 0.2picoamperes (pA) (Bi+) average current at the sample holder. A bunchpulse of a 0.7 ns duration resulted in mass resolution (M/DM)> 8000. A200×200 mm² area is rastered by primary ions to obtain the SIMS spectrawhile maintaining the ion dose about 10^12 ions cm⁻². The negative ionmass spectra are internally calibrated using C—, CH—, C₂H—, and C₄H—peaks.

The results of Table 3 and FIG. 9 confirm that the nanocrystal ofExample 2-1 include an In—F₂ bonding (whose peak is detected at m/z152.900) and Zn—F bonding. The XPS spectrum confirms the presence of theZn—F bonding, and thus it may be understood that in the nanocrystal ofExample 2-1, the fluorine is present at an interface of the InP core andthe ZnS shell.

TABLE 3 TOF-SIMS sample InP InF InF₂ ZnS ZnF InP/ZnS (ComparativeExample 1) O X X O X InP/ZnS(F) (Example 2-1) O X O O O

The quantum yields of the nanocrystals of Examples 2-1 to 2-12 andComparative Example 1 are evaluated.

To this end, using a spectrometer (manufactured by Hitachi Co. Ltd.,model name: F-7000), a photoluminescence spectrum is obtained for thenanocrystal particles prepared in Example 2-1 and Comparative Example 1and the results are shown in FIG. 4 . The results of FIG. 4 confirm thatthe semiconductor nanocrystals of Example 2-1 has a very high quantumyield of 73 % at a wavelength of 618 nm in comparison with thenanocrystal of Comparative Example 1 having a quantum yield of 31 % at awavelength of 624 nm. The quantum yield may be improved by at leastabout two times.

The quantum yields and the wavelength of emitted light (nm) at themaximum QY for the nanocrystals of Examples 2-1 to 2-4 and ComparativeExample 1 are summarized in Table 4.

TABLE 4 Comp. Example 1 Example 2-2 Example 2-1 Example 2-3 Example 2-4Quantum yield (%) 31% 69 % 73 % 73 % 66 % Wavelength of emitted light(nm) 624 618 618 618 627

The results of Table 4 confirm that the nanocrystals of Examples 2-1 to2-4 have greatly improved values of the quantum yield in comparison withthe nanocrystal of Comparative Example 1.

Table 5 shows the quantum yields of the nanocrystals of Examples 2-5 to2-8 and Example 2-12 and Comparative Example 1.

TABLE 5 Comp. Example 1 Example 2-5 Example 2-6 Example 2-7 Example 2-8Example 2-12 Quantum yield (%) 31% 64% 66 % 50% 63 % 85%

The results of Table 5 confirm that the nanocrystals of Examples 2-1 to2-8 and Example 2-12 have greatly improved values of the quantum yieldin comparison with the nanocrystal of Comparative Example 1.

Table 6 shows the quantum yields of the nanocrystals of Examples 2-9 to2-11 and Comparative Example 1.

TABLE 6 Comp. Example 1 Example 2-1 Example 2-9 Example 2-10 Example2-11 Quantum yield (%) 31% 73 % 57 % 42% 64%

Referring to Table 6, the sequence of introducing the reactants maycontrol the quantum yield of the nanocrystals, and the nanocrystals ofExamples 2-1 and 2-9 to 2-11 have greatly improved values of the quantumyield in comparison with the nanocrystal of Comparative Example 1.

Example III Example 3: Preparation of InP/ZnSe(F) Nanocrystal

An InP/ZnSe(F) nanocrystal particle is prepared in the same manner asset forth in Example 2-1, except that 2.4 mmol of Se/TOP is used insteadof S/TOP.

Comparative Example 2: Preparation of InP/ZnSe Nanocrystal

An InP/ZnSe nanocrystal particle is prepared in the same manner as setforth in Example 2-1, except that HF is not used and 2.4 mmol of Se/TOPis added instead of S/TOP.

Evaluation III

For the nanocrystals of Example 3 and Comparative Example 2, thephotoluminescence spectrums are obtained in the same manner asEvaluation II and the results of the quantum yield and thelight-emitting wavelength at the maximum efficiency are shown in Table7.

TABLE 7 Comp. Example 2 Example 3 InP/ZnSe InP/ZnSe(F) Quantum yield (%)21 40 Light emitting wavelength of the maximum efficiency (nm) 642 637

Referring to Table 7, the nanocrystals of Example 3 shows greatlyimproved value of the quantum yield in comparison with the nanocrystalof Comparative Example 2.

Example IV Example 4: Preparation of InP/ZnSeS(F) Nanocrystal

An InP/ZnSeS(F) nanocrystal particle is prepared in the same manner asset forth in Example 2-1, except that 1.2 mmol of Se/TOP is usedtogether with 1.2 mmol of S/TOP.

Comparative Example 3: Preparation of InP/ZnSeS Nanocrystal

An InP/ZnSe nanocrystal particle is prepared in the same manner as setforth in Example 2-1, except that HF is not used and 1.2 mmol of Se/TOPis added together with 1.2 mmol of S/TOP.

Evaluation IV

For the nanocrystals of Example 4 and Comparative Example 3, thephotoluminescence spectrums are obtained in the same manner asEvaluation II and the results of the quantum yield and thelight-emitting wavelength at the maximum efficiency are shown in Table8.

TABLE 8 Comp. Example 3 Example 4 InP/ZnSeS InP/ZnSeS(F) Quantum yield(%) 35 50 Light emitting wavelength of the maximum efficiency (nm) 619621

Referring to Table 8, the nanocrystals of Example 4 shows greatlyimproved value of the quantum yield in comparison with the nanocrystalof Comparative Example 3.

Example V Example 5: Preparation of InP/ZnF₂ Nanocrystal

An InP/ZnF₂ nanocrystal particle is prepared in the same manner as setforth in Example 2-1, except that S/TOP is not used.

Example 6: Preparation of InP/ZnS/ZnS(F)

An InP/ZnS/ZnS(F) nanocrystal particle is prepared in the same manner asset forth in Example 2-1, except that the InP/ZnS nanocrystal obtainedin Comparative Example 2 is used instead of the InP nanocrystal.

Evaluation V-1

The crystalline structure of the nanocrystal particle obtained inExample 5 is confirmed.

An XRD analysis is made in the same manner as set forth in Evaluation IIand the results are shown in FIG. 8 , which confirms the presence of theZnF₂ crystal. A TOF-SIMS analysis is made in the same manner as setforth in Evaluation II and the results are compiled in Table 9, whichconfirms the presence of ZnF bonding.

TABLE 9 TOF-SIMS Sample InP InF InF₂ ZnS ZnF Comp. Example 1 InP/ZnS O XX O X Example 5 InP/ZnF₂ O X X X O

For the nanocrystal particle of Example 6, the results of the ICP-AESconfirm the formation of a ZnS(F) shell. In this case, fluorine is notpresent at the interface between InP and ZnS but is present in the outerZnS shell.

Evaluation V-2

The photoluminescence spectrums of the nanocrystals prepared in Examples5 and 6 are obtained in the same manner as Evaluation II and the resultsare shown in Table 10.

TABLE 10 Example 5 Example 6 InP/ZnF₂ InP/ZnS/ZnS(F) Quantum yield (%)49 60

Referring to Table 10, the nanocrystals of Examples 5 and 6 shows anenhanced quantum yield.

Example VI Example7: Preparation of InP/ZnS(Cl) Nanocrystal Particles

InP/ZnS(Cl) nanocrystal particles are prepared in the same manner as setforth in Example 2-1, except that HCl is used instead of HF.

Evaluation VI

An XPS analysis is made in the same manner as set forth in Evaluation IIand the results show that the nanocrystal particle of Example 7 includeschlorine in an amount of 1 % based on the amount of Zn. The PL spectrumof the nanocrystal particle of Example 7 is obtained in the same manneras set forth in Evaluation II, and it show that the quantum yield of theInP/ZnS(Cl) nanocrystal of Example 7 is about 36 %, which is higher thanthat of InP/ZnS by 5 %.

Comparative Example 4: ZnS Shelling After the HF Etching

The InP cores prepared in Reference Example 1 are dispersed in a mixedsolution of 0.14 mmol HF (in water) and 1.5 ml TOA, and irradiated withUV for 10 minutes. Ethanol is added thereto to cause precipitation ofthe nanocrystals, which are then separated by centrifugation andre-dispersed in toluene.

1.2mmoL (0.224 g) of zinc acetate, 2.4 mmol (0.757 g) of oleic acid, and10 mL of trioctylamine are placed in a flask, subjected to a vacuumstate at 120° C. for 10 minutes, and then heated to 280° C. after theatmosphere in the flask is exchanged with N₂. A toluene dispersion ofthe InP core being treated with HF as above is added thereto within 10seconds, and 2.4 mmol of S/TOP is added thereto and the reactionproceeds for 120 minutes. After that, the reaction mixture is rapidlycooled to room temperature and acetone is added thereto to producenanocrystal particles, which are then separated by centrifugation anddispersed again in toluene.

The quantum yield of the nanocrystal thus obtained is measured inaccordance with the same manner as Evaluation II, and the resultsconfirm that no substantial increase is found in quantum yield. The XPSanalysis, the EDS analysis, and the TOF-SIMS analysis may confirm thatno fluorine is present in the nanocrystal thus obtained. A TEM-EDSanalysis is made in the same manner as set forth in Example II and theresults are shown in FIG. 10 and FIG. 11 , confirming that fluorine doesnot exist in the nanocrystals as prepared.

Example 7: An InZnP Core and a Multi-Layered Shell With Using FluorineProduction of an InZnP Core

0.2 mmol of indium acetate, 0.125 mmol of zinc acetate, 0.6 mmol ofpalmitic acid, and 10 mL of 1-octadecene are placed into a reactor andheated at 120° C. under vacuum. The atmosphere in the reactor issubstituted with nitrogen after one hour. After heating at 280° C., amixed solution of 0.15 mmol of tris(trimethylsilyl)phosphine (TMS3P) and1 mL of trioctylphosphine is rapidly added thereto and reacted for 20minutes. The reaction solution is rapidly cooled to room temperature andadded with acetone and centrifuged to provide a precipitate, which isthen dispersed in toluene.

A Multi-Layered Shell Formation on the InZnP Core With Fluorine

A shelling process is used to form a multi-layered shell comprising Zn,Se and S. Specifically, 1.2 mmoL (0.224 g) of zinc acetate, 2.4 mmol(0.757 g) of oleic acid and 10 mL of trioctylamine are placed in a flasksubjected to a vacuum state at 120° C. for 10 minutes and then heated to280° C. after the atmosphere in the flask is exchanged with N2. Atoluene dispersion of the InZnP semiconductor nanocrystal prepared aboveis added thereto within 10 seconds, and a predetermined amount of S/TOPand a predetermined amount of Se/TOP is added several times at apredetermined time interval (each time with a varying ratio between theS/TOP and Se/TOP) to form a multilayered shell (with each layer having adifferent composition). During the shell formation, 0.14 mmol of HF (inan aqueous solution) in trioctylamine (TOA, a carrier solvent) isquickly injected.

After the completion of the reaction, the resulting mixture is rapidlycooled to room temperature and acetone is added thereto to producenanocrystal particles, which are then separated by centrifugation anddispersed again in toluene.

The total used amount of S and Se are 0.16 mmol and 2.8 mmol,respectively.

From the XPS analysis made by using the same apparatus set forth in theoriginal specification, it is confirmed that the resulting semiconductornanocrystal particle includes fluorine.

Comparative Example 5: InZnP Core/Multilayered Shell

A semiconductor nanocrystal including an InZnP core and a multi-layeredshell without using fluorine is prepared in the same manner as inExample 7, except for omitting the injection of the HF solution.

From the XPS analysis made by using the same apparatus set forth in theoriginal specification, it is confirmed that the resulting semiconductornanocrystal particle does not include fluorine.

Evaluation VII: Photoluminescent Analysis of the Core-ShellSemiconductor Nanocrystals

A photoluminescence spectrum is obtained using a spectrometer(manufactured by Hitachi Co., Ltd., model name F-7000) for thecore-multilayered shell semiconductor nanocrystal with the fluorinedoping of Example 8 and the core-multilayered shell semiconductornanocrystal of Comparative Example 5. The results are summarized in theTable 1. In Table 1, Full-Width-at-Half-Maximum is abbreviated “FWHM,”and Quantum Yield is abbreviated “QY.”

TABLE 1. Photoluminescent properties Peak Wavelength FWHM QY Example 7~530 nm 41 nm 68% Comparative Example 5 ~520 nm 54 nm 37%

The nanocrystal of Example 7, which was identical to the nanocrystal ofComparative Example 5, with the exception that the nanocrystal ofExample 7 included fluorine doping, provided a 79% improvement inquantum yield (37% to 68%) and a 13 nm improvement in FWHM, a 24%improvement.

Reference Example 2: Preparation of ZnSe Core

Selenium is dispersed in trioctylphosphine (TOP) to obtain a 2 M Se/TOPstock solution.

10 mL of trioctylamine is added to a reactor along with 0.125 mmol ofzinc acetate, 0.25 mmol of palmitic acid, and 0.25 mmol of hexadecylamine and the mixture is heated under a vacuum at 120° C. In one hour,an atmosphere in the reactor is converted into nitrogen.

After being heated at about 300° C., the prepared Se/TOP stock solutionis rapidly added to conduct a reaction. After 60 minutes, the reactedsolution is cooled to room temperature and acetone is added thereto tomake a precipitate, which is then centrifugation and dispersed intoluene.

UV-vis spectroscopy analysis and photoluminescence spectroscopy analysisof the obtained ZnSe semiconductor nanocrystal are performed. Theresults confirm that the obtained semiconductor nanocrystal has a firstabsorption maximum wavelength of about 400 nm and a maximum peakemission wavelength of about 420 nm.

Reference Example 3: Preparation of ZnSeTe Core

A ZnSeTe core is prepared in substantially the same manner as set forthin Reference Example 2 except that tellurium is dispersed intrioctylphosphine (TOP) to obtain 0.1 M Te/TOP stock solution and theSe/TOP stock solution and the Te/TOP stock solution are rapidly added ata Te/Se ratio of 1/25.

UV-vis spectroscopy analysis and photoluminescence spectroscopy analysisof the obtained ZnSeTe semiconductor nanocrystal are performed. Theresults confirm that the obtained semiconductor nanocrystal has a firstabsorption maximum wavelength of about 420 nm and a maximum peakemission wavelength of about 460 nm.

Example 8: A Multi-Layered Shell Formation on the ZnSe Core With UsingFluorine

1.8 mmoL of zinc acetate, 3.6 mmol of oleic acid, and 10 mL oftrioctylamine are added to a flask and vacuum-treated at 120° C. for 10minutes. The inside of the flask is substituted with nitrogen (N₂) andthen a temperature is increased to 180° C. The ZnSe core prepared inReference Example 2 is quickly added thereto. Then, at a temperature ofabout 320° C., a predetermined amount of S/TOP and a predeterminedamount of Se/TOP are added several times at a predetermined timeinterval (each time with a varying ratio between the S/TOP and Se/TOP)to form a multi-layered shell including Zn, Se, and S, each layer havinga different composition. During the shell formation, 0.14 mmol of HF (inan aqueous solution) in trioctylamine (TOA, a carrier solvent) isquickly injected.

After the completion of the reaction, the resulting mixture is rapidlycooled to room temperature and acetone is added thereto to producenanocrystal particles, which are then separated by centrifugation anddispersed again in toluene.

The total used amount of S and Se are about 1.0 mmol and about 0.3 mmol,respectively.

From the photoluminescence analysis result, it is confirmed that theproduced quantum dot has a maximum light emitting peak of 443 nm andquantum efficiency of over 60%.

Comparative Example 6: A Multi-Layered Shell Formation on the ZnSe CoreWithout Using Fluorine

A multi-layered core/shell nanocrystal particle is prepared insubstantially the same manner as set forth in Example 8 except for notusing the HF.

From the photoluminescence analysis result, it is confirmed that theproduced quantum dot without fluorine in the shell has a similar maximumlight emitting peak wavelength but its quantum efficiency issignificantly lower than that of the Core/Shell nanocrystal particle ofExample 8.

Example 9: A Multi-Layered Shell Formation on the ZnTeSe Core With UsingFluorine

1.8 mmoL of zinc acetate, 3.6 mmol of oleic acid, and 10 mL oftrioctylamine are added to a flask and vacuum-treated at 120° C. for 10minutes. The inside of the flask is substituted with nitrogen (N₂) andthen a temperature is increased to 180° C. The ZnTeSe core prepared inReference Example 3 is quickly added thereto. Then, at a temperature ofabout 320° C., a predetermined amount of S/TOP and a predeterminedamount of Se/TOP are added several times at a predetermined timeinterval (each time with a varying ratio between the S/TOP and Se/TOP)to form a multi-layered shell including Zn, Se, and S, each layer havinga different composition. During the shell formation, 0.14 mmol of HF (inan aqueous solution) in trioctylamine (TOA, a carrier solvent) isquickly injected.

After the completion of the reaction, the resulting mixture is rapidlycooled to room temperature and acetone is added thereto to producenanocrystal particles, which are then separated by centrifugation anddispersed again in toluene.

The total used amount of S and Se are 0.6 mmol and 0.08 mmol,respectively.

The results of the photoluminescence analysis are shown in FIG. 12 .

From the photoluminescence analysis result, it is confirmed that theproduced quantum dot has a maximum light emitting peak of 465 nm with aFWHM of 42 nm and quantum efficiency of 55 %.

Comparative Example 7: A Multi-Layered Shell Formation on the ZnTeSeCore Without Using Fluorine

A core/shell nanocrystal particle is prepared in substantially the samemanner as set forth in Example 9 except for not using the HF. Theresults of the photoluminescence analysis are shown in FIG. 13 .

From the photoluminescence analysis result, it is confirmed that theproduced quantum dot without fluorine in the shell has a maximum lightemitting peak of 466 nm with a FWHM of 44 nm and quantum efficiency ofabout 34 %.

While this invention has been described in connection with what ispresently considered to be practical exemplary embodiments, it is to beunderstood that the invention is not limited to the disclosedembodiments, but, on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A nanocrystal particle comprising at least onesemiconductor material and at least one halogen element, wherein thenanocrystal particle has a core-shell structure including a corecomprising a first semiconductor nanocrystal; and a shell surroundingthe core and comprising a crystalline or amorphous semiconductormaterial, and wherein the at least one halogen element is present asbeing doped therein or as a metal halide, wherein the at least onehalogen element comprises fluorine, wherein the fluorine is included inan interface between the core and the shell, in the shell, or in theinterface between the core and the shell and in the shell, wherein thefirst semiconductor nanocrystal of the core or the crystallinesemiconductor material of the shell comprises a Group II-VI compound, aGroup III-V compound, or a combination thereof, wherein the nanocrystalparticle has a quantum yield of greater than or equal to about 50%,wherein the crystalline or amorphous semiconductor material of the shellcomprises a composition different from that of the first semiconductornanocrystal of the core, and wherein the nanocrystal particle does notinclude cadmium.
 2. The nanocrystal particle of claim 1, wherein thefluorine is present at an interface of the core and the shell, and inthe shell.
 3. The nanocrystal particle of claim 1, wherein the firstsemiconductor nanocrystal of the core, the crystalline semiconductormaterial of the shell, or both comprises zinc.
 4. The nanocrystalparticle of claim 3, wherein the first semiconductor nanocrystal of thecore comprises ZnSe, ZnS, or a combination thereof.
 5. The nanocrystalparticle of claim 4, wherein the first semiconductor nanocrystal of thecore further comprises tellurium.
 6. The nanocrystal particle of claim3, wherein the crystalline semiconductor material of the shell comprisesZnS, ZnSe, ZnSeS, or a combination thereof.
 7. The nanocrystal particleof claim 1, wherein the nanocrystal particle comprises a bond betweenzinc and the fluorine.
 8. The nanocrystal particle of claim 7, whereinthe nanocrystal particle comprises a Zn—F bond, as determined bytime-of-flight secondary-ion mass spectrometry.
 9. The nanocrystalparticle of claim 1, wherein the shell is a multi-layered shellcomprising an inner shell, an outer shell on the inner shell, a firstinterface between the core and the inner shell, and a second interfacebetween the inner shell and the outer shell, each comprising acomposition different from one another and wherein each is independentlycrystalline or amorphous, and wherein the halogen element is included ina region selected from the inner shell, the outer shell, the firstinterface, and the second interface, and a combination thereof.
 10. Thenanocrystal particle of claim 1, wherein the at least one halogenelement is included in an amount of greater than or equal to about 0.05mole percent, based on the molar amount of the metal included in thecore of the nanoparticle.
 11. The nanocrystal particle of claim 1,wherein the shell comprises a material having a bandgap which is largerthan a bandgap of the first semiconductor nanocrystal.
 12. Thenanocrystal particle of claim 1, wherein the nanoparticle furthercomprises a ligand compound coordinating a surface of the nanocrystalparticle.
 13. The nanocrystal particle of claim 12, wherein the ligandcompound comprises a compound represented by RCOOH, RNH₂, R₂NH, R₃N,RSH, R₃PO, R₃P, ROH, RCOOR′, RPO(OH)₂, or R₂P(O)OH, or a combinationthereof, wherein R and R′ are each independently selected from a C1 toC24 alkyl group, a C2 to C24 alkenyl group, and a C6 to C20 aryl group.14. A process for synthesizing a nanocrystal particle of claim 1, theprocess comprising: obtaining a first mixture including a firstprecursor comprising the second metal, a ligand compound, and a solvent;heating the first mixture; contacting a source of fluorine, a secondprecursor, and the core comprising the first semiconductor nanocrystalwith the first mixture, which is heated, to obtain a second mixture; andheating the second mixture to a reaction temperature to react the firstprecursor and the second precursor to obtain a nanocrystal particlecomprising a semiconductor material and the fluorine.
 15. The process ofsynthesizing a nanocrystal particle of claim 14, wherein the firstprecursor comprising the second metal is in a form of an elementalmetal, an alkylated metal compound, a metal alkoxide, a metalcarboxylate, a metal nitrate, a metal perchlorate, a metal sulfate, ametal acetylacetonate, a metal halide, a metal cyanide, a metalhydroxide, a metal oxide, a metal peroxide, or a combination thereof,wherein the second precursor comprises a Group VI element comprisingsulfur, selenium, or tellurium, a compound comprising the Group VIelement, or a combination thereof, and wherein the source of the halogenelement is selected from HF, NH₄F, HBF₄, an ionic liquid including ahalogen, and a combination thereof.
 16. The process of synthesizing ananoparticle of claim 14, wherein contacting the source of the halogenelement with the first mixture comprises dissolving the source of thehalogen element in a carrier solvent to obtain a solution and adding thesolution to the first mixture, and wherein the carrier solvent isselected from water, a ketone, a primary amine, a secondary amine, atertiary amine, a heterocyclic compound having a nitrogen atom, a C6 toC40 olefin, a C6 to C40 aliphatic hydrocarbon, a C6 to C30 aromatichydrocarbon substituted with a C1 to C20 alkyl group, a primary,secondary, or tertiary phosphine substituted with a C6 to C22 alkylgroup, a primary, secondary, or tertiary phosphine oxide substitutedwith a C6 to C22 alkyl group, an aromatic ether, an aromatic alcohol,and a combination thereof.
 17. A device including the nanocrystalparticle of claim
 1. 18. The device of claim 17, wherein the device is alight emitting diode, an organic light emitting diode, a sensor, a solarcell, an imaging sensor, or a liquid crystal display.